It is a worrying time for anyone concerned about the future of the planet. In the past few weeks a string of authoritative reports have told us that carbon emissions are hitting record levels, and that without urgent action the world is headed for warming of 4◦C or more. The World Bank has set out just how catastrophic such levels of warming will be for nature and all parts of human society.
We are already seeing how vulnerable the world is to a changing climate. Just this year we have seen a dramatic decline in Arctic sea ice, a series of extreme weather events and soaring food prices - often linked to droughts and floods. Climate change is no longer an abstract future threat, it is on our doorstep.
The alarm bells are ringing louder than ever. But the lack of response from the world's political leaders is baffling - and will certainly seem so to future generations. There are some positive signs. President Barack Obama has said that he will make climate change and clean energy one of his three priorities for his second term. But the world should expect more from its leaders.
In the UK, we are lucky to have a prime minister who has promised leadership on climate change.
In 2006, WWF took David Cameron to the Arctic to see first-hand the impacts of a warming world. On his return, he spoke passionately about the need for a cross-party consensus, and helped to secure the UK's world-leading Climate Change Act. In 2008, Mr Cameron promised that "we are not going to drop the environmental agenda in an economic downturn... It's not that we can't afford to go green - it's that we can't afford not to go green." And when he arrived in Downing Street in 2010, Mr Cameron famously pledged to lead "the greenest government ever".
Worryingly, Mr Cameron appears to have gone cold on climate change. He has made no major speech on the issue since becoming prime minister. His government deserves credit for progress on issues such as setting up the Green Investment Bank. But other voices in Mr Cameron's party, including Chancellor George Osborne, are now opposing strong action on climate change and renewable energy.
Important decisions on a target to clean up the UK's power sector by 2030 and on tackling emissions from aviation and shipping have been deferred until after the general election. The Chancellor is backing a new dash for gas which will blow a hole in the UK's carbon targets, and appears to be pushing for a weakening of the important fourth carbon budget. Ironically, the disarray in government policy is causing great concern to businesses seeking invest in renewable energy - one of the few bright spots for the UK's economic recovery.
Today, WWF and 24 other NGOs and charities are delivering a Christmas card to 10 Downing Street - by husky sled, naturally. We are urging Mr Cameron to rediscover his leadership on climate change and clean energy. We hope that he will throw his weight behind renewable energy, and help kick-start a green industrial revolution that will help the UK's economy.
The UK is ideally placed to lead on the low-carbon agenda, thanks to our Climate Change Act and huge renewable energy resources. It is also uniquely placed to help break the low-ambition stalemate that is holding back action around the world. The UK is ideally placed to help catalyse this. But as foreign secretary William Hague said earlier this year, "when trying to persuade other countries to go green, it is a huge advantage to be able to point to the example we are setting at home". But neither can happen without clear political leadership.
So Mr Cameron, we hope that this New Year you will remember your trip to the Arctic - and make a resolution to reassert your commitment to strong action on climate change in 2013, both at home and abroad.
Follow Dr Keith Allott on Twitter: www.twitter.com/@KeithAllott